Apparatus for drilling rate logging



Dec. 12, 1944. D. SILVERMAN ET AL APPARATUS FOR DRILLING RATE LOGGING 2Shets-Sheet 1 Filed Ju1y25, 1940 v INVENTORS: 91(7/[8/051/1/(37/177117Lfor/ e54.

Filed July 25, 1940 2 Sheets-Sheet 2 IN VENT CR5 1 luea/vnan I 5 272 7'Patented Dec. '12, 1944 APPARATUS FOR DRILLING RATE LOGGING DanielSilverman and Robert W. Stuart, Tulsa,

Okla., assignors to Stanolind Oil and Gas Company, Tulsa, Okla., acorporation of Delaware Application July 25, 1940, Serial No. 347,569

3 Claims.

This invention relates to the art of logging wells during the drillingthereof and more particularly to a method and apparatus for loggingwells being drilled b the rotary method involving the measurement of therate at which the drill bit penetrates the various strata encountered.

For many years Well drillers operating rotary rigs have been able todiscern to a limited extent by the behavior of the rotating mechanismwhen there has been a change in the nature of the formation beingdrilled, and some efforts have been made to systematize and obtainpermanent records of this sort of information. For example, spaced markshave been made on the Kelly joint, and the time required to drill adistance equal to the interval between them noted. Furthermore, the sameprinciple has been applied to an automatically recording system in whicha mark is made on a clock-driven chart for each foot or other selecteddistance of hole drilled, so that a measure of drilling rate is obtained. In another system the position of the Kelly joint or travelingblock is recorded on a chart moving at a constant speed, thus providingdata for the calculation of drilling rate.

The systems mentioned above and other similar ones have a number ofdisadvantages, among which are the following: (1) The desired type ofrecord is not obtained and calculation is necessary to make it readilyunderstandable. (2) Prior methods have not been truly automatic in thatthey require manual manipulation or subsequent interpretation toeliminate the errors which would otherwise arise during the addition ofnew stands of pipe and similar operations. (3) Prior systems have givenno direct indication of drilling rate which is the primary quantity itis desired to evaluate. The best possible log is one in which thedrilling rate is plotted directly against the depth of the bit andprovision for obtaining such a g is a feature of our invention.

Our invention comprises a system of drilling rate logging which is freefrom the disadvantages enumerated above and gives an accurate log of therelative rates of drilling through the various strata traversed by thedrill bit. Furthermore, it includes a preferred form in which thedrilling rate is recorded in terms of revolutions of the drill bitrather than in terms of time. since the rate of penetration per unit oftime may be meaningless if the speed of rotation varies more than asmall amount.

It is therefore an object of our invention to provide a novel method andapparatus for obtaining a log of the drilling rates at which a rotarydrill bit penetrates the various formations encountered during a rotarywell drilling operation. Another object is to provide com-' pletelyautomatic apparatus for making such a log and for making it in a formimmediately understandable and usable. Still another object is toprovide apparatus for recording a log of the rate of drilling perrevolution of the drill bit. A further object is to provide apparatusfor drilling rate logging giving a record wherein drillin-g rate isplotted directly against depth. Further objects, advantages and uses ofour invention will be apparent from the following detailed descriptionread in conjunction with the drawings, in which:

Figure 1 illustrates diagrammatically one form of apparatus according toour invention as applied to a conventional rotary rig;

Figure 2 represents a modified drilling rate logging apparatus accordingto our invention, and

Figure 3 shows schematically a further modification falling within thescope of our invention.

In one of its broad aspects our invention comprises the production of anindication of the rate of drill bit penetration into the formation beingdrilled as a function of the number of revolutions of the drilling bitand recording that indication on a medium moving with a velocityproportional to the rate of bit penetration with respect to time. Inthis way the drilling rate can be recorded directly against indiciarepresenting the depth at which the drill bit is located. Preferably thedrilling rate indication is of a type such that no computation orinterpretation is necessary in order to make it usable. In other words,theindication should be such that its amplitude is responsive to thetrue drilling rate. Examples of methods of carrying out the above willbe described hereinafter and in the course of that description manyimportant details of our invention will be fully brought out.

Referring now to Figure 1, the upper portion of a well II] is shownwhich is being drilled by the rotary method. The rotary drillingapparatus is conventional and is shown in very simplified form. Thisapparatus includes a derrick structure ll having a floor l2 and mountedon foundation members l3. having a drill bit (not shown) at its lowerend and Kelly joint l4 and mud swivel [5 at its up-- per end issupported from the upper portion of derrick II by means of bail l6, hookl1, travel A string 'of drill pipeling block l8, crown block l9 andcable 20. One end of cable 20 is wound upon draw works drum 2| and asshown, the other end, known as the dead line, is wound upon drum 22,.although it can be merely anchored to some portion of the derrickstructure. Mounted upon derrick floor I2 is a rotary table 23 for thepurpose of rotating Kelly joint I4 and hence the entire drill string.

It is deemed unnecessary to describe the operation of drilling, addingnew stands of drill pipe, etc. since all of these operations arewell-known to those skilled in the art. As mentioned above, however, therate of penetration per revolution of the drill bit into the formationbeing drilled and hence the rate at which the Kelly joint or travellingblock is lowered per revolution of the drill bit is a quantity whichbears a significant relationship to the nature of that formation. Inorder to measure this drilling rate it is therefore essential to providesome means of following the downward movement of the drill string. Thereare a large number of methods available for accomplishing this but apreferred method is shown by Way of example in Figure l. A wire line 24is attached at its lower end to travelling block l8 and passes over apulley 25 located substantially directly above travelling block l8 andthence to drum 26 upon which it is wound and which is provided with aspring having a strength sufficient to keep line 24 in slight tensionregardless of the position of travelling block l8. Obviously both drum26 and pulley 25 rotate in a manner dependent upon the vertical movementof travelling block l8 andhence of the entire drill string. We havechosen in this instance to utilize pulley 25 as the means for providingdepth indications and for this purpose a Selsyn transmitter 21 isillustrated connected to pulley 25. Any rotation of pullev 25 istherefore transmitted by means of transmitter 21 and conductors 26 and'10 to the correspondin Selsyn receiver 29 which is preferably located ashort distance away from the d i ling rig and which is utilized to drivethe rest of the logging apparatus according to this embodiment of ourinvent on.

It is apparent that Selsyn receiver 25 will rotate at a speed and in adirection corresponding to the ra sing and lowering of the travell ngblock I8, but in order to measure drilling rate it is desired merely toutilize the downward motion of the drill string and hence of travellingblock l8 when drilling is actually in progress. In order to accomplishth s, shaft 30 driven by Selsyn motor 29 is provided with means forpreventing the operation of the record ng apparatus except during theactual drilling. As shown. this means takes the form of a depth counter3| and a clutch 32. Clutch 32 is a magnetic clutch which is en a ed onlywhen electr cal current from battery 33 passes through its coils. andits purpose is to prevent the operat on of shaft 30 and the apparatusdriven thereby except when the movement of travelling block I8 isassociated with a corresponding movement of the entire drill string anddrill bit. This magnetic clutch can suitably be composed of an electromanet mounted on the shaft and provided with two b ushes suitablyinsulated from the case and attached to the coil contained within, and aflat ferromagnetic plate mounted on the corres onding assoc ated shaftin such a manner that it wi l rotate with the shaft but may be movedlongitudinally with respect to it. This last can be accomplished, forexample, by slotting the shaft and mounting the plate loosely on the shat with a pin going through the slot. In the present instance this isaccomplished by using a weight indicator 34 on the dead line which isarranged to actuate switch 35 through a hydraulic connection 36,whenever the load carried by cable 20, and hence that carried bytravelling block |8 exceeds a predetermined value.

The rotation of shaft 30, which is proportional to the vertical movementof the drill bit at any moment, actuates depth counter 3| which is of atype having a maximum revolution counter and preferably has an algebraiccounter as well. The algebraic counter is a simple direct driverevolution counter connected directly to shaft 30 and producing itsindications in the upper set of dials of depth counter 3|. Thus when therevolution of shaft 30 reverses, the reading on the upper set of dialsof the depth counter 3| decreases. The maximum revolution counter islikewise driven from shaft 30 by a pair of gears (not shown) and can be,for example, a rotary ratchet counter which revolves only in onedirection, being restrained from rotation in the opposite direction bythe ratchet enclosed therein. This maximum revolution counter producesits indications on the lower set of dials on depth counter 3|; forexample, depth counter 3| can be made up of a Veeder-Root counter N-245(direct drive revolution counter) to which is coupled a Veedcr- RootL-245 rotary ratchet counter, the two being mounted in a common case asis quite customary in the counter art. The revolution counter 3| byitself and without connection with. the rest of the apparatus of oursystem constitutes no change from the prior art. Such a dual typecounter involving an algebraic counter and a maximum revolution counteris shown, for example, in the Hayward U. S. Patent 2,166,212. Themaximum revolution counter then indicates the depth of the hole and thealgebraic counter the depth of the drill bit. It is, of course, notnecessary that counter 3| be of an indicating type, but only that ithave the maximum revolution counting feature described. Counter 3| isequipped with an output shaft 31 driven by the maximum revolutionmechanism and this serves two purposes. First, it actuates recorder reel'38 so that the recording medium actuated by reel 38 registers the depthof the well at a given time. Second, by means of a gear box 39 and shaft40 an electrical contacting device 4| is caused to close the circuitincluding battery 42 and rotary switch 43 momentarily with a frequencyproportional to the rate of drill bit penetration. Switch 43 ispreferably of the rotary telephone type having a large number ofcontacts 44, for example twenty-five or fifty such contacts. Such aswitch, for example, is shown on page 25, catalog 4071-3 of the AmericanAutomatic Electric Sales Company. These contacts 44 are connected tosuccessive points along a resistance 45 across which a battery 46 isshunted. It will be apparent that the resistance 45 and battery 46 forma voltage divider whereby the voltage applied across the recorder 49varies in accordance with the particular point along the resistance onwhich the arm 52 bears. Therefore, the amount of current flowing throughleads 4'' and 48 to recorder 49 depends solely upon the position of thearm 52 of rotary switch 43, that is, upon which of contacts 44 is inuse. Recorder 49 is provided with a pen arm 50 arranged in such a waythat the electrical variations impressed upon it are recorded uponrecording medium 5|, as the latter is moved by reel 38.

The operation of rotary switch 43 is such that each time on electricalcontact is made by contactor 4I, switch arm 52 is moved from one ofcontacts 44 to the next in a given direction. This is accomplishedbecause current flows through the upper solenoid 43a of rotary switch'43which thereby attracts the corresponding arm 43e of the step by stepfeed mechanism which moves the center ratchet wheel 43d one notch in acounterclockwise direction for each actuation of the solenoid 43a,against the action of spiral spring 430 attached to the ratchet wheel.When the lower solenoid 43b of this switch 43 is energized by passing onelectric current through conductors 53, the flexible release leverassociated with solenoid 43b is pulled downward, thus releasing theratchet wheel 43d permitting it to rotate under the influence of thespiral spring 43c in a clockwise direction, to its original position.'This position is against stop 43 Obviously, therefore, if arm 52 isreturned to its initial position at regular intervals, the maximumtravel of switch arm 52 and hence the maximum deflection of pen arm 50in each cycle will represent the drilling rate per unit of time andrecording medium will show a plot in which the drilling rate per unit oftime is plotted against the depth of the well. By suitably regulatingthe number of contacts may by contactor 4| per foot drilled this recordcan be made to have all of the usefulness of a smooth curve, although itis the maxima of the various deflections which are significant.

Generally, we prefer to obtain an indication'of the rate of drilling perrevolution of the rotary table rather than per unit of time, andapparatus for accomplishing this is shown in Figure 1. A second Selsyntransmitter 54 is arranged to rotate at a speed proportional to that ofrotary table 23 and is connected to Selsyn receiver 55 by means ofconductors 56, the latter in turn driving a rotary contactor 51 througha gear box 58. Contactor 51 is connected in series with battery 59 andconductors 53 so that each time the circuit is closed by contactor 51Switch arm 52 returns to its zero position and the number of contacts44.

traversed by switch arm 52 between each of these impulses appliedthrough leads 53 is a. measure of the drilling rate per revolution ofthe rotary table, and it is this quantity which is recorded on recordingmedium 5|.

It will be apparent from the above that We have provided a novel systemfor logging a well during the drilling thereof by the rotary method inwhich a record is obtained showing the rate of drilling through thevarious formations encountered. There are many other ways of achievingsubstantially the same results within the scope of'our invention and oneof these is shown in Figure 2, to which reference is now made. Forconvenience corresponding parts are designated by reference characterscorresponding to those shown in Figure 1.

The drilling apparatus proper is not shown since it may be the same asthat illustrated in Figure 1, the vertical movements of the drillstringbeing translated into corresponding rotational movements of Selsyn motor29 via conductors 28 and III in the manner already'described; ,Also, asin Figure 1, the motion of motor 29 is transmittedthrough shaft 30 anddepth counter 3| to a gear box 39, shaft 31 and reel 38 upon whichrecording medium 5| winds. However, in place of the clutch previouslydescribed for restricting the motion of the various parts of therecording anparatus to those times during which drilling is 3821RPM moreswitch in the field circuit of the Selsyntransmitter-receiver set. InFigure 2a portion fof this circuit is shown consisting of two conductorsI0 extending to theSelsyn transmitter (not shown),

with a switch H and a source of alternating current I2, such as an ACgenerator, connected across them. When switch 'II is open Selsynreceiver 29- will not follow the movements of the correspondingSelsyn'transmitter in the derrick and consequently suchoperations asadding new sections of drill pipe, reaming, replacing drill bits, etc.can be carried on without causingany motion of the recording system.Switch II can be located in any convenient place in the vicinity ofthedrilling rig, one excellent location being near the clutch pedalcontrolling the rotationof the rotary table, this arrangement being suchthat the circuit is closed while the rotary table is operating, butotherwise is open. By means of this arrangement the switch IIwill'require little attention since the rotary table is seldom rotatedexcept when drilling is actually being carried on. Many alternativearrangements are, of course,

possible.

A differential I3 actuated from gear box 39 by shaft 14 drives twoshafts I5 and I6 which drive potentiometer arms I9 and 80, respectively.Potentiometer arms I9 and are urged to their zero positions by means ofsprings 8| and 82, and are alternately held in advanced positions bymeansof magnetic brakes 11a and 18a, respectively. These brakes can beany of the customary solenoid-operated brakes adapted to grip a shaftand prevent its rotation when current is applied through the solenoid.On shafts I5 and I5, between the beveled'gears and the brakes 11a and1811 are mounted magnetic clutches 11b and 18b, which can be, forexample, of the same type shown in Figure 1 and which operate in thesame fashion. When no electric current is passing through the coil ofeither of these magnetic clutches the corresponding shaft will bedisconnected from the potentiometer arm drive.

Shaft 83, which may be arranged to rotate at a constant speed or at 'aspeed proportional more rate of rotation of the rotary table carries arotary switch 84 having a number of contacts I20 to I21 respectively,arranged so that in each revolution thereof magnetic brakes Ila and 18aand magnetic clutches 11b and 181) will be actuated in the desiredmanner by means of battery and conductors 85, 81, 88, 89 and 90. Also,the arrangement is such that potentiometer arms'19 and 80 arealternately connected to recorder:- 49 by means of conductors 9|, 92-and 93, the potentiometers being energized by battery 94.

The operation of the apparatus. of Figure 2 is as follows: Assuming thatthe contacts of switch 84 are in position I and that potentiometer arm19 is in zero position, it will be seen that current from battery 85 isflowing through contact I28, contact I24 and" conductor 90, thusenergizing brake 18a. "At this instant no current is flowing throughcontact I2Ia so, that brake 11a is not energized. No current flowsthrough conductor 81; clutch 11b is not energized and arm I9 isdisconnected from shaft 15. Shaft 15 is likewise disconnected from arm80, since no current flows through conductor 89. Arm 80 is held in postion by brake 18a. As soon as switch 84'reaches pos tion 2, however, thecircuit including contacts I 20 and I22, conductor 81 and battery 85 ismade, magnetic clutch 'IIb connects'the potentiometer arm actuatingmechanism to shaft 'I5.and,, potentiometer arm I9 moves'fromits zeroposition as shaft I5 continues to rotate, thus attaining an increasingelectrical potential. This situation continues until switch 84approaches position 3, which may represent either a desired interval oftime or a predetermined number of revolutions of the rotary table. Whenswitch 84 reaches position 3, brake 18a is released, and arm 80 ispermitted to reassume a zero position under the influence of the spring82. During this time and until position I is reached, potentiometer armI9 is fixed in the most advanced position attained during the intervalof movement, since the contacts I20 and I22 no longer connect lead 81 toclutch I'Ib while brake 'I'Ia is connected during this period to thebattery 85 through conductor 88 and contacts I20 and I2I. The potentialof arm I9 is applied to meter 49 and recorded on recording medium 5| bymeans of pen arm 50. As is apparent from the drawing this isaccomplished by connecting conductors 9| and 93 when switch 84 reachesposition 3, and during the entire interval between positions 3 and I,the same value continues to be recorded. During the same interval, ofcourse, arm 80 returns to zero position and againis advanced by means ofclutch 18b, and v the potential corresponding to the most advancedposition attained by it will be recorded during the interval fromposition I to position 3. Finally, when switch 84 reaches position 4,current is caused to flow through conductors 86 and 89 thus completingthe cycle. apparent from a study of the contacts of rotary switch 84.

It is apparent that the record on medium 5| will show a plot of thedrilling rate versus the depth of the hole. By using a suflicientlysmall unit of time or rotation this record will be a continuous drillingrate curve. The same result can be achieved by other means. For example,Figure 3 illustrates a purely electrical method of recording drillingrate.

An electrical circuit is shown in Figure 3 which operates by recordingthe frequency of the elec--' trical pulses caused by the closing of. thecontactor 4| driven by shaft '40 and gear box 39, as in Figure 1. Theoperation of this circuit is as follows: Condenser I00 is charged bybattery |0I through resistance I02 and the accumulated charge is imposedupon the plate of Thyratron tube I03, the grid of which is biasednegatively by means of battery I09 through resistance I05. As is wellknown in the art, the Thyratron tube has the property of beingnon-conducting until the negative grid potential decreases to apredetermined value, dependent upon circuit conditions, whereupon thecurrent in the .platecircuit instantaneously rises to its maximum value,independent of the existing grid potential. 1 Current continues to flowin such tubes until the anode circuit is opened or the anode voltage islowered to a small value, whereupon the plate current suddenly ceasesuntil the tube is again activated by a decrease in grid potential.In-the present instance, therefore, each time contact is made bycontactor 4| the grid bias battery I09 is short-circuited, therebyreducing the negative bias to such a point that current instantaneouslyflows at its maximum value in the plate circuit of tube I03. In eachcase the plate current will consist of a definite charge, namely, thatwhich had been stored in condenser I00. That current which has passedthrough the plate circuit of the Thyratron tube I03 passes intocondenser I06 and then is further averaged with respect to time by meansof resistance I01 and condenser This cycle of operation is I08 andfinally passes to one coil 2 of the ratiometer-type recorder 49.

In order to produce a record of the drilling rate per revolution of therotary table it is only necessary to add a similar circuit operating oncontactor 51 driven in proportion to the rate of rotation of the rotarytable, and to apply the output from this circuit to the other coil ofthe ratio type meter 49. Thyratron tube I I0 is fired by contactor 51and the averaged current therefrom is impressed upon coil III ofrecorder 49 while the averaged current from tube I03 is impressed uponcoil II2. The currents from the Thyratron tubes are applied to coils IIIand H2 in such a sense that the deflections produced by these currentsare in opposite directions. Obviously the position assumed by thesecoils and by pen arm will be determined by the ratio between thefrequencies with which contacts are made by contactors 4| and 51 andhence by the bit penetration per revolution of the rotary table.

While we have described our invention in terms of certain specificembodiments thereof we do not desire to be limited thereto but only bythe scope of the appended claims.

We claim:

1. Apparatus for recording the rate of penetration of a drill bitthrough formations penetrated in the course of a rotary drillinoperation per unit number of revolutions of said bit, including meansfor advancing a record strip proportional to the descent of said drillbit, means for producing a series of electric impulses in directproportion to the number of revolutions of said drill bit, meansactuated by descent of said drill bit for producing an electric currentvarying directly in average amplitude with the descent of said drillbit, means for recording on said strip a quantity varying directly withsaid current, and means controlled by said impulse producing means forperiodically limiting the recorded amplitude on said strip.

2. Apparatus for logging a Well during a rotary drilling operationcomprising means for advancing a record strip proportional to thedescent of the drill, an electrical circuit including a resistance, anarm makin contact with said resistance at one of a plurality ofpositions thereon, means for recording on said record strip anindication of the position of said arm on said resistance, means formoving said arm in accordance with the descent of the drill during saidrotary drilling operation, and means actuated by the rotation of thedrill and adapted to return said arm to its zeroposition each time thatsaid drill rotates a predetermined amount.

3. Apparatus for logging a well during a rotary drilling operationcomprising means for advancing a record strip proportional to thedescent of the drill, an electrical circuit including a resistance, anarm making contact with said resistance at one of a plurality ofpositions thereon, means for recording on said record strip anindication of the position of said arm on said resistance, means forproducing electrical impulses in accordance with the descent of thedrill bit, means actuated by each of said impulses for moving said armby one position in a given direction, and means actuated by the rotationof the drill and adapted to return said arm to its zero position eachtime that said drill bit rotates a predetermined amount.

DANIEL SILVERMAN. ROBERT W. STUART.

